The present invention relates to locking means for locking spools of a dual spool safety belt retractor employed in association with safety belts and harnesses employed for restraining passengers in seats of moving vehicles. More particularly, the present invention relates to a pawl locking means interposed between two spools of a dual spool retractor in operative locking relation to ratchet wheels provided on the spools to lock the spools against protractive rotation in response to actuation by a single inertia sensor and, more specifically, to an improved construction for the pawl means and the means for mounting such pawl means to the retractor.
Dual spool automatic emergency locking safety belt retractors have been developed heretofore for use in automotive vehicles to automatically lock a pair of safety belts wound about the dual spools in an emergency condition encountered by the vehicle. In some instances the retractor is mounted between the vehicle seats with the seat belts serving two separate safety belt systems for the two front seat passengers of the vehicle. In other situations, the dual spool retractor may be used for storing ends of two safety belt webbing portions employed in a single safety belt harness employed for restraining a single passenger in his vehicle seat in the case of an emergency condition. It is common to sense such emergency conditions through the use of a vehicle inertia sensor, generally of the pendulum type, which reacts in response to vehicle acceleration or deceleration of more than a predetermined amount to activate the locking means employed for locking the spools of the retractor against further belt protractive rotation. It has also been common to use a unitary pawl disposed between the two spools with the sensor moving the pawl into engagement with at least one of the spool ratchet locking means and the rotation of such first spool causing the unitary pawl member to be shifted or moved into locking engagement with the other spool ratchet means.
Prior art examples of dual spool automatic locking retractors which employ a single locking pawl means between two spools of a dual spool emergency locking retractor are found in U.S. Pat. Nos. 3,960,339; 3,974,979; 4,065,070; 4,135,683; and 4,164,336. In these prior art patents, a single pawl is provided between two spools of the retractor with the lockup of one end of the pawl with one spool causing the pawl to be moved into locking engagement with the other spool. The single pawls employed have been provided with a "floating" support as in U.S. Pat. No. 4,135,683 or a resilient mounting by end bushings as in U.S. Pat. No. 3,960,339 in order to improve the locking characteristics of the single pawl employed between the two spools.
It is been recognized that where a single double ended pawl is employed, as in the aforementioned prior art patents, there is the possibility that the pawl may experience a false latching condition if the pawl tooth ends, of either end, engage the tip of a tooth on the associated spool locking ratchet normally employed in locking the spools. These patents have disclosed means for mounting the unitary, double ended pawl in a floating or resilient mounting in order to improve the locking characteristics of the pawl during such false latching conditions. One such means is the addition of a program pawl and ratchet formed of resilient material which is engaged by motion of the inertia sensor and causes engagement of a spool locking pawl and ratchet in a predetermined or programmed manner. We have determined that there is room for improvement in the locking characteristics of an emergency locking means for such dual spool retractors employing a single inertia sensor and single pawl means and therefore, as a primary object of the present invention, desire to disclose and provide such an improvement in the locking characteristics of such double ended pawl means for dual spool retractors.